The question of planning permission for a skylight comes down to a short list of measurements and a few facts about the building. A tape measure and the house's paperwork settle a good deal of it before anyone goes near the roof. The rules here are the ones for England, and they apply to ordinary houses: flats, houses converted under change-of-use permitted development and listed homes follow different routes.
Rooflights and roof windows on a house are covered by a national allowance called permitted development, which means the permission is already granted by the rules, so you do not have to apply for it. The allowance has edges, and the limits mark them. The separate Building Regulations side of a roof opening is covered in our Building Regulations guide for skylights, and the shorter questions for individual roof types are answered elsewhere on the site, such as whether a roof window needs permission.
The allowance for roof windows and rooflights
For a house, the rule sits in Class C of Part 1 of Schedule 2 to the General Permitted Development Order, which you can read on legislation.gov.uk. It treats an extra roof window or rooflight as a small alteration to the roof and grants permission for it, provided the work stays inside three limits. Each limit is a measurement, so each can be checked on site.
How far the unit stands out
Take the surface the tiles or slates form on the original roof: the unit, frame included, may rise 150 mm above it at most. A roof window bedded into the slope sits close to that surface and normally falls inside the limit. A unit on a raised kerb adds its kerb height, its frame and its glass to the figure, and that sum is what gets measured.
How high it sits
The top of the new unit must also stay level with or below the original roof's high point. On a pitched roof this rarely matters for a roof window set into the slope, but it can come into play near a ridge, or where a unit stands up from a low slope beside a taller part of the roof.
Windows in a side slope
Any window on a roof slope that forms a side elevation of the house must be obscure-glazed, and it must be non-opening unless the parts that open are more than 1.7 m above the floor of the room it is in. On a hipped roof, the slope at the end of the house can form a side elevation. A bathroom or landing window placed in the hip is the kind of opening that condition is aimed at. A window in the main back slope is not caught by it.
The word original appears in two of the three limits. It means the roof as it was first built, or as it stood on 1 July 1948 if the house is older than that. A loft extension added in the 1980s has not moved the baseline, so the height and projection are still measured against the roof the house started with.
Measuring the 150 mm
The 150 mm counts from the surface of the original roof slope to the highest point of the unit, frame included. A figure taken from the glass alone will look better than the true one.
Lanterns and rooflights on flat roofs
Building Regulations draw a line between a roof window and a rooflight, and it is a useful line for planning too. The Approved Document L glossary defines a rooflight as a glazed unit set out of plane with the roof surface, raised on a kerb or upstand, and counts a roof lantern as one. A roof window instead follows the roof's own orientation and lies in plane with it.
On a pitched roof the roof window is the usual choice, and it lies within a few centimetres of the slope. On a flat roof of a rear extension, a garage or a porch, the glass sits on an upstand, and the upstand has to be high enough to throw water clear and carry the roof covering up its sides. Add the unit above it and a roof lantern usually stands more than 150 mm proud. That normally puts it outside Class C, so an application is needed unless the council confirms otherwise.
A low flat rooflight on a shallow upstand is a closer call, since the measurement includes the frame as well as the upstand. We take the real dimensions at the survey instead of working from a catalogue figure. If the lantern was shown on the drawings of an extension that already has planning permission, it is covered by that approval, so the first document to find is the decision notice for the extension. The lantern guides cover the detail in roof lantern planning and Building Regulations and, for flat roofs generally, planning permission for a flat roof skylight.
| Unit | How it sits | Planning position |
|---|---|---|
| Roof window | In plane with the surrounding roof | Normally inside the 150 mm limit |
| Rooflight on a kerb | Out of plane, on an upstand | Measured, frame included, against 150 mm |
| Roof lantern | A rooflight standing well above the roof | Usually over 150 mm, so usually an application |
Buildings that have no householder rights
Class C belongs to dwellinghouses, and some homes are not dwellinghouses in the sense the order uses. A flat or maisonette has no householder permitted development rights, so a rooflight above a top-floor flat needs planning permission whatever its size. The freeholder's consent, or the management company's, is a separate question under the lease, and it can be harder to get than the council's.
The same goes for houses created by converting offices, shops, barns and similar buildings under the change-of-use permitted development rules. The conversion gave the building a new use without a full planning application, and it did not hand over the ordinary householder rights with it.
Rights taken away by a condition
A council can remove permitted development rights from a house by putting a condition on the planning permission for it. The condition has to be written into the decision. If your house was built, extended or converted under a recent permission, the decision notice is the document to read, and the council publishes it on its planning register. Wording that removes rights usually refers to the General Permitted Development Order and to specific Classes. A house that was never touched by a condition keeps Class C.
Check this one, because nobody can assume the answer. Two neighbouring houses of the same design can differ, one with its rights intact and one without, if the second was built later under a different permission. We ask for the decision notice at survey when the house or its extension dates from a recent permission.
| Building | Householder rights | Route for a rooflight |
|---|---|---|
| House with no restricting condition | Yes, within the three limits | Measure the unit against the limits |
| Flat or maisonette | None | Planning application, plus the freeholder's consent |
| House converted under change-of-use permitted development | None | Planning application |
| House with a condition removing rights | Removed, as the condition words it | Read the decision notice, then apply |
Conservation areas, Article 4 directions and listed homes
Living in a conservation area does not by itself remove Class C. A roof window that meets the three limits is still permitted development on a house there. What can take the right away is an Article 4 direction, a notice a council makes for a defined area that withdraws named permitted development rights. Directions are written for particular works in particular streets, so the exact wording and the map matter, and the council's planning pages are where to find both.
When a direction does cover roof alterations, a roof window that would otherwise be permitted needs a planning application. We cover the process in Article 4 and rooflights and in the guide to conservation area rooflight planning, and flat, slim-framed units suited to those roofs are described under conservation rooflights.
Listed buildings
A listed house keeps its Class C rights on paper, but listing brings a second regime, listed building consent, which covers alterations that affect the character of the building. A new or altered roof window will almost always need that consent. The listed building consent application is where the unit, its position and the method of fixing get judged. The roof covering, the rafters and the roof's shape can all be part of what is protected, and a council conservation officer reads each application against that. Our page on rooflights on listed buildings goes further.
If your house is listed, expect the unit, the position and the method of fitting to all be part of the application.
Terms on a planning decision
- Permitted development
- Work that has planning permission granted by national rules, so no application is needed.
- Article 4 direction
- A council notice that withdraws named permitted development rights in a defined area.
- Listed building consent
- A separate approval for alterations that affect a listed building's character.
- Original roof
- The roof as first built, or as it stood on 1 July 1948 for an older house.
- Decision notice
- The council's written outcome for an earlier application, listing any conditions.
Getting a firm answer from the council
You do not have to guess. If you think a rooflight is permitted development and want it confirmed in writing, you can apply to the council for a lawful development certificate, which records that the work is lawful on the facts you gave. If the unit is outside Class C, you apply for planning permission, and a householder application is the usual form for a single house. Both are made through the Planning Portal, and the fee and the drawings required are listed there.
The decision on either belongs to the council, so no installer can promise one. An application needs a plan of the roof, the position of the opening and the dimensions of the unit, and our survey measurements give you those. Any certificate or decision notice you receive is worth keeping with the house papers for a future sale.
If the work is a replacement for a unit that is already in the roof, the same limits are tested against the new one. A like-for-like swap in the same opening normally stays inside the dimensions of the old unit, but a replacement lantern that is taller than the one it replaces changes the answer.
What we check at the survey
The planning questions form part of the survey. We take these on the roof and at the house, and we write them up with the quote so you can see what applies. The final word on any application sits with the council.
Planning points taken at the survey
- Projection and height The unit's frame and kerb measured against the original roof slope and the ridge.
- Slope direction Whether the planned position is on a slope forming a side elevation, where the obscure-glazing and non-opening condition applies unless the parts that open are more than 1.7 m above the floor of the room.
- Type of building House, flat, conversion or listed, since each has a different starting point.
- Area and history Conservation area, any Article 4 direction, and conditions on past permissions.
The 1.7 m height is measured from the floor of the room, not from the ceiling.
Planning is only half the paperwork
Permission from the council to alter the outside of a house does not cover how the work is built. A new opening also goes through Building Control, which looks at the structure around the hole and the heat loss of the glazing, and where it applies, fire safety. That is a separate notification with a separate sign-off. We handle the Building Control notification where the work is notifiable, and the details are in the Building Regulations guide.
Costs on a roof opening are explained at our costs page, and the starting point for the roof you have is the guide to putting a skylight into an existing roof. To have your own house checked against the limits above, book a free survey or send photos to us on WhatsApp at 07880 284133.
